6533b7d4fe1ef96bd1261d69

RESEARCH PRODUCT

Numerical, dimensional or mixed progression disease to imatinib as prognostic factor in patients with metastatic GIST.

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11040 Background: The majority of GIST patients with advanced disease initially achieves disease control from imatinib treatment. Approximately 10% of patients progresses within 6 months of starting therapy (primary resistance) and also 50-60% of the responding patients develops progression disease within two years (secondary resistance). Progression disease (PD) can be numerical, dimensional or mixed. The known prognostic factors of risk stratification in local disease are tumor size, mitotic activity and anatomic site. In this retrospective analysis we explore several clinical factors affecting survival in metastatic setting. Methods: The population included in this large database of 128 patients with metastatic GIST was obtained examining data collected from four Oncologic Centres with expertise for the GIST management. The clinical factors analyzed were sex, tumor size, mitotic activity, anatomic site, KIT and PDGFRa mutational status, site of metastasis, FDG-PET status at progressing disease and pattern of tumor progression to I line imatinib 400, II line Imatinib 800 or Sunitinib, evaluated with CT scan or MRI: PD with dimensional growth (dimensional, dPD), with new lesions appearance (numerical, nPD) and with both numerical and dimensional growth (Mixed, mPD). Every factor has been correlated with Overall Survival (OS) measured in months. Survival analyses were performed by using the Kaplan-Meier method. Univariate and multivariate Cox proportional hazard regression models were executed to search for association with the outcome. Results: Univariate analysis showed significant value for primary tumor site (p < 0.0001), mitotic activity (p = 0.02), tumor size (p = 0.05) and PD pattern (p = 0.008): OS nPD group was 102.7 months, in dPD group 87 and in mPD group 70. The multivariate analysis confirm significant prognostic factors for OS tumor site (p = 0.0004) and PD pattern (p = 0.02). Conclusions: with the limitations of a retrospective analisys, this study shows for the first time the impact of pattern of progression on OS: patients with dPD have a worse prognosis than those with nPD or mPD, suggesting type of PD as an independent prognostic factor for OS in advanced GISTs.